1. Field of the Invention
The present invention relates to a double resonance coil arrangement for a magnetic resonance device of the type having at least two coils, each formed by a coil conductor in which at least one capacitor as well as at least one inductor forming an oscillating circuit with a further second capacitor are connected.
2. Description of the Prior Art
If, for magnetic resonance data acquisition, nuclei other than hydrogen are to be excited and their signals received, for the purpose of spectroscopy or imaging for instance, it is advantageous to employ a detection coil arrangement that is sensitive both to hydrogen nuclei as well as to other types of nuclei (called X-nuclei below). It is then possible for instance to firstly re-cord a hydrogen overview image for localization purposes and then to execute X-nuclei spectroscopy or X-nuclei image data acquisition for instance. Such coil arrangements with two discrete resonance frequencies are known as double resonant coil arrangements.
To obtain a double resonant coil, it is known to connect an inductor having a second capacitor (i.e., in addition to the “already” present first capacitor) arranged in parallel thereto in the coil conductor. This generates an oscillating circuit, which acts in addition to the oscillating circuit formed from the coil conductor itself and the first capacitor.
Several coils are usually used in a coil arrangement. Decoupling techniques are known in order to decouple these coils from one another so that said coils do not mutually influence one another. It is known to geometrically decouple coils. To this end, a specific overlap between adjacent coils is generated, which is measured such that the magnetic flow permeating through the overlap region offsets the magnetic flow generated in the other regions by the other coils in each instance. Galvanic decoupling arrangements are also known. In this way, the galvanic components, for instance inductive components, are used between the coils. The galvanic decoupling arrangement nevertheless functions properly only in a very narrow frequency band, so such a decoupling arrangement can be realized only for one frequency. In addition, a complicated balancing process for the final decoupling is necessary. Lastly, decoupling by means of transformers is known. Transformers enable coils to be decoupled without a direct connection.
If decoupling by transformers is used with a double resonant coil arrangement, additional components are needed to generate the double resonance and also for de-coupling purposes. This adversely affects the quality of the coils. The open circuit-load quality ratio has a direct impact on the signal-to-noise ratio of the coil.